President Barack Obama celebrated the spirit of compromise Friday as he signed a controversial $858 billion tax cut and unemployment insurance extension into law — but warned that bipartisan comity could be fleeting.

The bill, the result of a deal Obama cut with Senate Republicans over the objections of many Democrats, was a major victory for a White House that spent much of the past two years battling a unified GOP on the stimulus and health care reform.

"We are here with some good news for the American people this holiday season," Obama told about 150 people, including Senate Majority Leader Mitch McConnell (R-Ky.), gathered in the Eisenhower Executive Office Building.

Noticeably absent were Speaker-to-be John Boehner (R-Ohio), Senate Majority Leader Harry Reid (D-Nev.) and House Speaker Nancy Pelosi (D-Calif.), who were all cut out of initial negotiations between Obama’s staff and McConnell.

The president — who is still pushing for legislation repealing the “don’t ask, don’t tell” ban on gays serving openly in the military and the ratification of a new START treaty by the Senate in the remaining days of the lame-duck session — hailed the new law as a “good deal” for taxpayers and called for the spirit of compromise to continue into 2011, when a much more conservative 112th Congress is sworn in.

“Now, candidly speaking, there are some elements of this legislation that I don’t like,” said Obama, who abandoned his demand that the cuts be applied only to families earning less than $250,000 in the face of unified GOP opposition. “There are some elements that members of my party don’t like. There are some elements that Republicans here today don’t like. That’s the nature of compromise — yielding on something each of us cares about to move forward on what all of us care about.”

Yet, Obama said he foresaw times “over the next couple of years, in which the holiday spirit won’t be as abundant as it is today. Moreover, we’ve got to make some difficult choices ahead when it comes to tackling the deficit. In some ways, this was easier than some of the tougher choices we’re going to have to make next year. There will be times when we won’t agree, and we’ll have to work through those times together. But the fact is, I don’t believe that either party has cornered the market on good ideas. And I want to draw on the best thinking from both sides.”

If the bill hadn’t passed, the tax bill for the average American taxpayer would have risen by about $3,000, he noted.

Vice President Joe Biden, who negotiated key elements of the deal with McConnell on Obama’s behalf, introduced the president with a reference to his now-famous, caught-by-the-mike quip about Obama’s passage of health reform being a “big f—-ing deal.”

“Ladies and gentlemen, this is a — I wasn’t going say, a big deal, but an important deal. I can no longer say ‘big deal.’ Thank god, my mother wasn’t around.”

The measure extends the Bush-era tax cuts for all Americans for two years while also extending unemployment benefits for 13 months. It also includes one-year payroll tax cuts and other incentives to help working families, small businesses and college students. None of it is paid for, raising the hackles of fiscal conservatives, and it provides an estate tax break for wealthy property owners, a GOP-inserted provision that sparked a near-revolt by House liberals.

McConnell was one of five Republicans present at the bill-signing ceremony, along with 19 Democrats and others, including Treasury Secretary Timothy Geithner, the Rev. Al Sharpton and outgoing National Economic Council Chairman Larry Summers.

The event was Obama's 29th public bill-signing ceremony, according to The Associated Press.